Overload circuit breaker



Nov. 20, 1923 1,474,693

F. TOBIEN OVERLOAD CIRCUIT BREAKER Filed March 27, 1922 2 Sheets-Sheet l Nov. 20, 1923.

- F. TOBEEN OVERLOAD CIRCUIT BREAKER Filed March 27. 1922 2 Sheets-Sheet 2 Patented Nov. 20, 1923. V

UNITED STATES PATENT OFFICE.

FELIX TOBIEN, OF ESSEN', GERMANY, ASSIGNOR TO FRIED. KRUPP .AKTIENGESELL- SCHAFT, OF ESSEN-ONTHERUHR, GERMANY.

I OVERLOAD CIRCUIT BREAKER.

Application filed March 27, 1922. Serial No. 547,262.

To all whom it may concern: p

Be it known that I, FELIX ToBiEN, residing at Essen, Germany, a citizen of the German Republic, have invented a certain new and useful Improvement in Overload Circuit Breakers, of which the following is a specification.

This invention relates to improvements in overload circuit-breakers of the type in which the movable contact member is placed under the action of a power accumulator,

of a releasing and of a holding coil, such as disclosed for example in the United States application, Serial No. 533,895, of February 3 1922.

The present invention has for its object to provide an overload circuit-breaker ot' the character stated which is adapted for the protection of a plurality of motors which can be connected selectively in series or in paralleland which is of a variable sensibility conforming itself to the kind of connection of the motors.

lVith this end in view the invention consists in the arrangement, construction and combination of parts to be herein described and particularly pointed out in the appended claims.

-The drawings diagrammatically show, by way of example, an overload circuit-breaker which is designed to protect two main current motors which are controllable by a con troller.

In the drawings:

Fig. 1 is a diagram of the series connection of the two motors at the beginning of the starting operation;

Fig. 2 is the same diagram at the end of the starting operation;

Fig. 3 is a diagram of the parallel connection ofthe motors, the starting resistance being in an intermediate position;

Fig. 4 is a diagram of the connection 01 the controller with the overload circuitbreaker and the other elements of the circuit.

Referring now to the drawings, in which similar characters of reference indicate the same parts, it will be seen from the electrical connections shown in Figs. 1 and 2, that the main current releasin coil a which forms part of the overloa circuit-breaker and which encircles a magnet core B, is con nected by one of its ends through a trolley a with the current feeding line A, while its other end has conductive connection with one, a of the two stationary contact-points a a of the overload circuit-breaker. The contacts a a can be bridged by a movable contact member?) which is carried by the magnet core B. The magnet core B is put under the action of a spring 0 which constitutes a power accumulator tending to hold the magnet core in closing position. Connected with the other contact a of the overload circuit-breaker are the multiple step starting resistance a and the two main current motors a a and a a The two motors are in series and the field winding a of the motor a a is grounded. D is the second magnet winding or holding coil of the overload circuit-breaker. It is connected by one end to the trolley a; its other end is connected b a conductor F through a series resistance and an auxiliary switch f to the connection between the second motor 6%" a and the earth. Placed between the magnet coil D and the contact a is another resistance E which is proportioned so that, when the overload circuit-breaker is open, the magnet coil D is energized by an exciting current of a strength which will suflice to hold the circuit-breaker in open position contrary to the action of the spring C. This holding action of the coil D is secured even when the full starting resistance a is switched in. i g

The diagrams of connections illustrated in Figs. 1 and 2 only differ from each other inasmuch as in Fig. 2 the entire starting resistance a is cut out and the auxiliary switch is closed, while in Fig. 1 the start ing resistance. a is switched in and the auxiliary switch 7 is open. Provision is made, in a manner to be described hereinafter, for automatically executing the opening and closing motions of the auxiliary switch f during the switching out and in of the starting resistance a the arrangement being such as to cause the auxiliary switch 7, when the motors are in series, to move from open to closed position shortly before the end of the starting operation and to immediately return to open position upon re-commencing the switching-in of the starting resistance. As a result thereof, the magnet coil D is now charged by an exciting current the strength of which depends on the value of its own resistance and on that of the series resistance G. The magnet coil D will there fore boost the magnet field of the overload circuit-breaker so that the sensibility of the latter with regard to overload will be in: creased. 7

According to the diagram shown in Fig. 3 about half the starting resistance a is cut out, the auxiliary switch 7' is open and the motors a a and a a are now connected in parallel. The magnet coil 1) will not furnish any additional magnetic contribution to the magnetic field of the overload circuit-breaker.

According to Fig. ll a controller K is employed for performing the several switching operations, said controller having conncction with the overload circuit-ln'eaker, the starting resistance a the motors a c and a? a the auxiliary switch and the earth. The auxiliary switch 7 is constructed as a wiper which co-operates with a con.- tact bar (71: of the controller K. The contact bar is of such length and arranged on the rotary portion oi the controller in such a manner that it will enter into contact with the co-operating wiper 7' shortly before the starting operation of the series-connected motors is being finished (Fig. and that it will again leave the wiper f as soon as the transition from the connection in series (Fig. :2) to the connection in parallel (Fig. 3) takes place. The action of this arrangement will therefore be that the auxiliary switch is only closed in a position of the controller K corresponding to the series connection of the motors towards the end of the starting operation, while it is open in all other positions of the controller.

lVhen starting the motors c a and c when connected in series (Fig. 1), the auxiliary switch f is open and the sensibility of the overload circuit-breaker is comparatively small, since its magnetic field is excited only by the main current releasing coil D. Only upon finishing the starting operation (Fig. 2), the auxiliary switch 7' will be automatically closed and will thus cause an increase oi? the sensibility of the overload circuit-breaker to an extent depending on the size of the series resistance G. If the charging rate oil? the releasing coil. of is again increased by the. transition from the series connection into the parallel connection of the motors (Fig. 3), the auxiliary switch f will open again automatically and the sensibility of the overload circuit-breaker will be reduced to the same amount which it possessed during the starting period of the motors when connectthe current-system when the normal charg-- ing rate is slightly exceeded.

Ii the overload circnit-ln'eaker has interrupted the circuit of the motors a? a. and (4 in consequence of an overload, the motors can be switched in again only by moving the controller K into a position in which the main current circuit as well as the branch circuit containing the auxiliary switch 7' are broken.

Claims:

1. The combination with an electromagnetic overload circnit-breaker for a plural ity of motors to be selectively connected in series or in parallel, comprising two stationary contact-points, a movable contact member adapted to be acted upon by a power accunnilator, a releasing coil and a holding coil, of a controller and an auxiliary switch, said holding coil being placed in a branch circuit line adapted to be put under the full voltage oi the current feeding system and the auxiliary switch being adapted to close the said branch circuit line towards the end of the starting operation ot the motors when in series connection.

The combination with an electromag netic overload circuit-ln'eaker :tor a plurality 0t motors to be selectively connected in series or in parallel, comprising stationary contacts and a movable contact member adapted to be acted upon by a power accumulator, a releasing coil and a holding coil, of a controller, a. contact bar on the con troller and a wiper adapted to CO-OPOI'zttO with the said contact bar, the said contact bar and the wiper constituting an auxiliary switch, and the contact bar being arranged on the controller so as to cause the auxiliary switch. to be closed in a position. or the controller correspmnling to the series connec tion olthe motors towards the end of the starting operation and to remain open in all other positions of the controller.

The foregoing specification signed at Essen, Germany, this 17th day 01 February, 1922.

FELIX TOBIEN. 

